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Java > Open Source Codes > org > apache > mina > handler > chain > IoHandlerCommand


1 /*
2  * Licensed to the Apache Software Foundation (ASF) under one
3  * or more contributor license agreements. See the NOTICE file
4  * distributed with this work for additional information
5  * regarding copyright ownership. The ASF licenses this file
6  * to you under the Apache License, Version 2.0 (the
7  * "License"); you may not use this file except in compliance
8  * with the License. You may obtain a copy of the License at
9  *
10  * http://www.apache.org/licenses/LICENSE-2.0
11  *
12  * Unless required by applicable law or agreed to in writing,
13  * software distributed under the License is distributed on an
14  * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15  * KIND, either express or implied. See the License for the
16  * specific language governing permissions and limitations
17  * under the License.
18  *
19  */
20 package org.apache.mina.handler.chain;
21
22 import org.apache.mina.common.IoSession;
23
24 /**
25  * <p>A {@link IoHandlerCommand} encapsulates a unit of processing work to be
26  * performed, whose purpose is to examine and/or modify the state of a
27  * transaction that is represented by custom attributes provided by
28  * {@link IoSession}. Individual {@link IoHandlerCommand}s can be assembled into
29  * a {@link IoHandlerChain}, which allows them to either complete the
30  * required processing or delegate further processing to the next
31  * {@link IoHandlerCommand} in the {@link IoHandlerChain}.</p>
32  *
33  * <p>{@link IoHandlerCommand} implementations typically retrieve and store state
34  * information in the {@link IoSession} that is passed as a parameter to
35  * the {@link #execute(NextCommand,IoSession,Object)} method, using custom
36  * session attributes. If you think getting attributes is tedious process,
37  * you can create a bean which contains getters and setters of all properties
38  * and store the bean as a session attribute:</p>
39  *
40  * <pre>
41  * public class MyContext {
42  * public String getPropertyX() { ... };
43  * public void setPropertyX(String propertyX) { ... };
44  * public int getPropertyZ() { ... };
45  * public void setPropertyZ(int propertyZ) { ... };
46  * }
47  *
48  * public class MyHandlderCommand implements IoHandlerCommand {
49  * public void execute( NextCommand next, IoSession session, Object message ) throws Exception {
50  * MyContext ctx = session.getAttribute( "mycontext" );
51  * ...
52  * }
53  * }
54  * </pre>
55  *
56  * @author <a HREF="mailto:dev@directory.apache.org">Apache Directory Project</a>
57  * @version $Rev: 555855 $, $Date: 2007-07-13 12:19:00 +0900 (금, 13 7월 2007) $
58  */
59 public interface IoHandlerCommand {
60     /**
61      * <p>Execute a unit of processing work to be performed. This
62      * {@link IoHandlerCommand} may either complete the required processing
63      * and just return to stop the processing, or delegate remaining
64      * processing to the next {@link IoHandlerCommand} in a {@link IoHandlerChain}
65      * containing this {@link IoHandlerCommand} by calling
66      * {@link NextCommand#execute(IoSession,Object)}.
67      *
68      * @param next an indirect reference to the next {@link IoHandlerCommand} that
69      * provides a way to forward the request to the next {@link IoHandlerCommand}.
70      * @param session the {@link IoSession} which is associated with
71      * this request
72      * @param message the message object of this request
73      *
74      * @exception Exception general purpose exception return
75      * to indicate abnormal termination
76      */
77     void execute(NextCommand next, IoSession session, Object JavaDoc message)
78             throws Exception JavaDoc;
79
80     /**
81      * Represents an indirect reference to the next {@link IoHandlerCommand} of
82      * the {@link IoHandlerChain}. This interface provides a way to forward
83      * the request to the next {@link IoHandlerCommand}.
84      *
85      * @author The Apache Directory Project (mina-dev@directory.apache.org)
86      * @version $Rev: 555855 $, $Date: 2007-07-13 12:19:00 +0900 (금, 13 7월 2007) $
87      */
88     public interface NextCommand {
89         /**
90          * Forwards the request to the next {@link IoHandlerCommand} in the
91          * {@link IoHandlerChain}.
92          */
93         void execute(IoSession session, Object JavaDoc message) throws Exception JavaDoc;
94     }
95 }
96
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